NetReload: netmodels for addNetwork

This patch defines the netwok entities that we use in oVirt:

- Bond,
- Bridge,
- Nic,
- Vlan

These entities are now responsible for their underlying devices for
the addNetwork step. In a following patch, they shall take
responsibility as well for network deleting.

Change-Id: Iba5c5b84760e27245cbe34c3b290c54e51278e72
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>